Process of producing steel in side-blown converters.



A n sas Parana, onnroia."

JOHN H. HALL, or nEw'YoRx, n. Y., assrcnon T TAYLon wnan'ron was a srnnn COMPANY, on 'HIVGH BRIDGE, new messy, A CORPORATION or new annsnr.

' rnoonss orrnonncmc srnnn IN SIDE-BLOWN convnn'rnns.

eanne's.

1\To Drawing.

zen of the United States, and resident of New York, in the county of New York and than in a bottom blown .over shall take place, as will tion to overcome.

State of New York, have invented certain new and usefullmprovements in Processes of Producing Steel in side Blown Converters, of which the following is a specifi cation. k

This invention relates to 'a pneumatic process of producing steel from cast iron together with steel scrap or other available forms of ferruginous material, and has in' view the oxidation of the carbon, SlllCOIl and manganese by lateral air blowing, the main feature being the regulation of the slag formed at successive stages of the operation, so that substantially no overflow or boiliiig now be explained, reference being had to the folloW-' ing specification and claims. 3

For many purposes it"is highly advantageous to use a side blown converter rather than a bottom blown one, owing'to the lower cost of the former and its accessories, and

for other purposes it is almost essential because in a side blown converter the metal may be brought up to a higher temperature hearth furnace. However, the use of a side blown comerter often is connected with certain difficulties not met within the use of ',a bottomblown converter and which difficulties it is the purpose of this inven- In a bottom blown converterthe material is vigorously agitated, so that 'the-action proceed uniformly, whereas ina side blown converter theag1tat1on is much less active,

from which fact great irregularity in operation often results, causing metal and slag to overflow or boil over from time to time, whereby loss of time and material and great inconvenience is occasioned. For this rea-- son the use of the side blown converter has been much restricted, especially in thetreatment of certain residues in which the man: ganese is relatively high inproportion to the silicon.

My process overcomes v these dlfiicult1es,

- thuswmaking side blown converters available where hitherto their use was impossible. I accomplish this result by acertain regulation in the quantity of the slag and Specification of Letters Patent. Application filed March 17, 1914.

one or in an openand manganese of the bath Patented nee. a, rare. Serial No. 825,404.

percentage of its constituents formed dur ing the operation. although at times iron is blown in Thus, these vessels which contains as much as .5% of manganese general rule it has been found that metal of which the silicon content is fromabout l to 2.5% cannot be blown without difiiculties if it 1% of manganese. that When the manganese content of such a mixture is above the figure. given, the overflow or boiling quently of metal from the converter is greater thanis the case when metal low in manganese is blown; and occasions not only serious inconvenience in the handling of the vessel,-but frequently a serious loss of metal.

The cause of the boiling over inaaside blown vessel appears to be as follows: When the silicon content of the mixture is such in proportion to the manganese content that the SiO,. resulting from the oxidation of the silicon by the blast of air, is considerably in excess of the molecular proportion of the Mn'O resulting from the oxidation of the manganese by the blast of air, the slag, which is composed essentially of SiO and Mn(), (plus a greater or less amount-of FeO resulting from the oxidation of some of the iron. of the metal), has so higha melting point that it is not freely fluid during the greater part of the bl w. i In the oxidation of the bath, the silicon and manganese of the surface layer are first oxidized, (approximately at the same time), and form-a slag composed largely of SiO andMnO. If the SiO so far exceeds the M110 that the slag is notfreely fluid at the temperature existing at thattime in the vessel, the slag combines with agreater or less amount ofFeO; the oxidation of iron to F eO occurringmore rapidly as the silicon are reduced; also as the' temperature rises; and asthe capacity of the slag for retaining FeO is greater or less,'-z'. c. the greater the excess of SiO over MnO, the greater the capacity of the slag for Fe(), and vice versa.

Thus in blowing metal 2% of silicon and 5% of manganese, the

or even more,' yet as a contains more than, about .8'to- The reason for this is containing say over of slag and freuntil the slagbecomes freely fluid; and as the carbon of the surface layers of the bath is oxidized to CO, both before the iron begins to oxidize in considerable quantities and also during the oxidation of the iron, more iron is oxidized and entersthe slag than could be the case if the slag were in constant contact with a metal containing a high proportion of carbon. The slag, therefore, becomes saturated with FeO, so that it is for the time being quite fluid and highly oxidizing,

As the bath of metal and slag is agitated to a considerable extent by the blast im pinging upon its surface at a slight angle, there is a tendency to mix the slag with the metal. When the slag is highly fluid this tendency is increased. Moreover, at the time when a great proportion of the silicon,

,manganese and carbon have, been oxidized from thesurface layers of the metal so that iron begins to be oxidized quite strongly, the carbon of the underlying portions of thebath will continue to be carried upward by. gravity, diffusion and convection, and

there will consequently be an increasein the content of carbon in the surface layer of the metal, When the carbon content of the surface layer is increasedin this way to a sufliciently high point, and when the slag,

I (which becomes very fiuid at about the same time),;is mixed with the surface metal by the action of the blast, a point is presently reached where a strong reaction begins to take place between the FeOof the slag-and the carbon of .the metal, according to the formula: FeO-l-C equals Fe-l-CO, (or some v y This reaction is often so violent. that it assists greatly in causing a,

large portion of the bathtobe violently agitated, and hence in a few moments after the reaction starts, a great deal of the metal is intimately named with theslag, and reacts Withit, so that a great Volume of CO is the vessel, and

generated and causes both metal and slag fill the upper portions of frequently to boil over, in greater or less amount, In these boilings, a loss frequently occurs not only of slag but also of metal. 5

This reaction, once started, continues until the FeO of the slag is reduced to such an extent that the slag loses its oxidizing power very largely, and is no longer freely fluid. A certain amount of the FeO will remain in the slag because. the affinity between the SiO of the slag and that percentage of Fe() to. froth up and too strong to be overcome by the affinityof' carbon for the'O of the lieO. Vhen this point'is reached the reaction ceases, the boiling subsides, and the bath, whose composition has been rendered more or less uniform by: the agitation produced by the boil, continues to be subjected to the oxidizing action .of the blast, which is always confined largely to that portion of the bath constituting the surface layer. The oxygen of (Example 2).

ving which the the blast again oxidizes silicon, manganese, carbon and iron, from the upper layer of the bath, and the same sequence of events tends to occur a second and sometimes a third, fourth or fifth time.

It is known that such melting point. It appears, moreover, that the relative" amounts of FeOland M110 present in the slag do not affect this ratio between the weight of SiO, and thesum of the weights of Fe() and'MnO, which gov- ,erns the composition of the slag of minimum melting point. This tendency of the slag to absorb F eO and MnOup to a certain sum, is offset to a greater or lessextent, by the tendency of the FeO of the slag to react with the carbon of thebath, as has been described. Hence, we see that if abath is treated containing'the usual high proportion'of silicon,

a slag as is produced in the Bessemer process is governed say 2%, and in addition manganese to the extent of some 1% (Example 1), a slag will be produced consisting of SlO ,'MIlO and FeO, which will become fluid upon the absorption of an amount of FeO less than the amount-necessary to render fluid the slag resulting from the oxidation of the silicon and manganese of a bath containing much silicon and very little. manganese, instance, 2% silicon and 60% manganese It is evident, therefore, that in blowing the first mixture, the period duroxidation of Fe from the metal and its absorption as FeO by the slag takes place, will beshorter than the corresponding period in the second mixture; be- .cause after the elimination of the silicon and manganese from the surface layer of the metal by oxidation has taken place, an amount of FeO will be absorbed sufficient to make the slag freely fluid and oxidizing;

and this amount of Fe() will be less in .Example 1, than in Example 2. The reac- 2, in which the manganese is about 5%, and

the silicon about 2%, because the silicon and manganese are oxidized from the metal approxnnatelyat the same time, and hence the total t1me. elapsing between the beginning of the blow and the time when the slag becomes freely fluid and oxidizing will be less in Example lthan in Example 2; be-

' cause less Fe need be oxidized to make the slag fluid, in Example l than in Example 2. The boiling, therefore, will take place I by experience that they will be violent and emma 7 and by the same reasoning, the period between the first and the second boils, and be tween the second and third boils, etc., will be similarly shorter in Example 1 than in Example 2. Hence, in blowing a bath suchas indicated in Example 1, the boils will ocwith silicon, manganese in proportion equal to or greater than those that have been found in the past to cause the explosive overflow which I have described. I have found by experiment that if'the proportions ofsilicon and manganese in the fluid bath of metal are such that a slag is produced by their oxidation to SiO and MnO which is freely fluid practically from the time when it begins to beformed, and such that the neo- Yes 9 of manganese, in all essary amount of heat is produced by their oxidation, the metal can beb, own in a side blown conyerter of any of' t without the serious explosive overflow or boiling over which, hitherto has accompanied the blowing ina side blown converter Off metal containing a considerable proportion previous experiments. In order to blow such a bath successfully,

--the. manganese and silicon must be in such proportion that the SiO, and HMO producedby their oxidation are in the proportion approximately: of SiO' 4;O%, and

. MnO-60%,

" requisite temperature.

i which corresponds practically to I molecules of SiO to 5 molecules of M110; and the amounts of silicon and manganese must be such as to produce suflicient e usual types.

earlier in Example 1 than in Example 2;

br even lower, and it may be as high as 2.5% or-even higher. But for any 'particular proportion of silicon in the bath,'the pro portion of manganese in the bath must be such that the slag resulting'from the oxidation of the silicon and manganese shall be freely fluid practically from the time it begins to be formed; and that the heat produced by the oxidation of'the silicon and manganese shall be sufficient to maintain the metal and. slag at the necessary tempera ture. Y

The proportion of the SiO, and MnO in the slag resulting from the oxidation of the silicon and manganese of the metal must be tion; and though heat to maintain both'metal and slag at the It must be understood that the exact proportion of SiO and MnO in the slag will vary according to the temperature existing in the vessel at the time,

- tors; so that it may be found that a proportion of -Mn() much lower, or much higher, than 60% maybe essentialin order that the slag may be fluid. I do not confine mself to exact proportions of SiO and Mn(), but

.vary' this proportion to suit the particular and with other fac-- case in such a way that the slag produced in the blowing shall be freely fluidlduring the greater part of the operation. a I do not con-fine myself, moreover, to any particular proportion of silicon in the bath;

the total amount of silicon, may be such as is ordinarily found in the metal treated in a side-blown vessel. It may be as low as 90% be so high that'at any such as to, result in a freely fluid slag; I have found that the proportions 40% SiO and 60% MnO are suitable in certain cases; but as already stated, to that exact proportion, and the MnO niay given temperature there is more of it present than that necessary toproduce a fluid slag; andif the conditions are such that a slag with less than 60% MnO will be fluid, I may use a much lower proportion of MnO in the slag.

In blowing such a mixture, it is evident I do not confine myself that after the silicon, manganese and carbon in' the surface layer of the metal are so far eliminated that the oxidation of iron in those layers begins to take place in considerable amount, the slag, which is already fluid, and in which there is already enough MnO to satisfy the SiO without the addition of much FeO, will react with the bath as soon as even a very small amount of, Fe() has been absorbed. This will be true because the slag being freely fluid, tends to mix with the metal throughout the opera cases iron will be slag as Fe() in apin some oxidized and enter the preciable amounts, before the carbon of the surface layer has become high enough by the mixing ofthe bath to react with the FeO of the slag; yet it has been found that the reaction takes place so early in the operation and at a time when the slag contains so little F e0, that the reaction does not result in the overflow ofslag and metal from the .converter. v

A further useful feature of this process is that advantage is taken of the heat of, combination of the manganese of the metal, in addition to the heat of the combination of the silicon of the metal, and this is utilized, in raising the temperature of the bath, and of course also of the slag.

The fluid slags, high in MnO, produced by blowing such mixtures as are the subject of this specification, are more severe upon of silica rock, mica schist, ganister or other i high in MnO or FeO, or both, as to corrode the lining in thismanner. In the bottom blown type of vessel, this wear upon the lining is naturally greatest at the surface charge, I may secure ofthe bath, where the slag comes in contact with the lining. The twyers being at the bottom of the bath, are less affected thanthe solid lining of the sides of the vessel,

which may be patched comparatively easily. In the side blown vessel, however, the twyers are placed in the sides of the vessel, and their mouths are more or happens that the portion of the .lining con taining the twyers is corroded to a considerable extent; and thus thetwyers and the lining at that point are sometimes cut away more rapidly than is the case in ordinary practice. Because the twyers must not be allowed to become shorter than a certain definite length, it may in some cases be necessary to repair the lining, especially at the twyers, more often high manganese mixtures than is the case in ordinary practice. The advantages secured by the-process, however, very much more than elf-set this trifling disadvantage in the-majority of cases.

the ingredients of the the desired amounts In v proportioning of manganese and silicon by theuse of a pig iron containing such proportions of the elements in questlon that it shall, a when melted, have the proper relative amounts of;

silicon and manganese; or I- may mix several pig irons containing varying proportions of silicon and manganese, 1n such rela tive amounts as to obtain the composition desired; or I may mix one or more such pig irons with appropriate amounts of iron or steel scrap in order to obtain the composition desired; or I may use in combinatreated may be taken from a blast furnace or blast furnaces directly, or may be melted of suitable amounts of term-manganese,

spiegeleisen, ferro-silicon silico-spiegel, or other similar alloy.- Again, I may obtain than that necessary for maxi-.

By charging to less immersed in the slag throughout the operation. Thus it iron containing 3.97%

in blowing these,

ment, as in any otherprocess. stated, the proportionsof 81116011 and man tions.

kinds of scrap, special varieties a considerable proportion of the manganese of thecharge by utilizingsteel scrap containing a high proportion of manganese. The exact proportions of these varying in? gredients ofthe charge, and of the silicon and manganese in those ingredients, is im-- material, s1nce it is generally a matter of simple arithmetic to so proportion ingredients of varying composition that the sum' total of the manganese and the silicon of the in cupola, so that a loss of silicon and manganese must be allowed for in melting the ingredients of the charge; I may it desirable to so proportion those ingredients that they shall contain an average of 2.03% of silicon and 5.34% of manganese. I the cupola 2,100 pounds of steel scrap containing 3% of silicon and 12% of manganese; 2,100 poundsof of silicon and-132% of manganese; 445 pounds of pig iron containing 2.07% of silicon and 3% of manganese; and 255 .pounds of steel scrap containing 30% ofsilicon and .75 oiimanganese, I shall secure in the mixture the average percentage of those elements desired. Of course theweight ofmetal charged to the cupola must be suiliciently greater-than the 4,500 pounds of fluid metal desired, to allow for thisloss'of silicon and manganese,

and also for the loss of a certaln amount of 1ron. As the losses in melting ma cupola are not the same inall cases,

rig;

it will not be possible to use the exact figures here given in every case; but the behavior of the cupola must be ascertained by experi- As' already ganese in this example are given as examples of compositions which will secure the desired results under the proper condi- Variations in the proportions and in the I total quantity of manganese and silicon may be made, provided that the total quantity is such as to generate suiiicient heat of combination to maintain theslag formed in a freely fluid state.

The metal or mixture of metals to be in a cupola in the vessel in which the air blowingtakes place, orin-any other known and suitable device.

What I claim as new is: m

.1. In the pneumatic process of making steel, the improvement which consists in subso proportioned that the slag produced by their oxidation shall approximate 60 parts parts of SiO and be;

, steel,

of Mn() "'toevry 40 workably fluid throughout the blow.

2; In the pneumatic process of making steel, the improvement which consists in subjecting to lateral air blowing a fer; ruginous mixture in which the silicon and manganese are present in such quantity and are so proportioned that by their oxidation there is produced a workably fluid slag con taining approximately 60 parts of MnO to every 40 parts of Slo 3. In the pneumatic process of making steel, the improvement which consists in subjecting to lateral air blowing, ferruginous material in which the silicon and manganese are present in such quantity and are so proportioned that the slag produced by their oxidation shall. contaln approximately 60 parts of MnO to every parts of SiO and that 'the power of the slag produced to retain FeO in combination is so limited that the FeO practically'as fast as formed reacts with the carbon of the metal, whereby the boiling of the bath is practically continuous andlthe tendency of the bath to boil over is substantially eliminated. p

4. In the pneumatic process of making steel, the improvement which consists in subjecting to lat ral air blowing, a mixture containing steel high in manganese, and pig iron, in which mixture the proportion of silicon to manganese is such that by their oxidation a slag is produced that contains approximately 60 parts of Mn() to every 10 that the power of parts of SiO and that is workably fluid practically throughout the blow.

5. In the the improvement which consists in subjecting to lateral air blowing, a mixture containing steel high in manganese, and pig iron, in which the silicon and manganese are present in such quantity, and are so proportioned that by their oxidation there is produced a workably fluid slag containing approximately 60 parts of MnO to every 40 parts of SiO,.

6. In the pneumatic process of making steel, the improvement which consists in subjecting to lateral air blowing, a mixture containing steel high in manganese, and pig iron, in which the silicon and manganese are resent vin such quantity and are so proportloned that the slag produced by their oxidation shall contain approximately 60 parts of MnO to every 40 parts of $0,, and

the slag produced to retain FeO in combination is so limited that the FeO practically as fast as formed reacts with the carbon of the metal, whereby the boiling of the bath is practically continuous and the tendency of the bath to boil over is substantially eliminate Signed at New York, in the county of New York and State of New York, this 16th day of March, A. D. 1914.

JOHN H. HALL.

Witnesses:

C. A. O. ROSELL, HowARo E, BROWN.

pneumatic process of making 

